When will my sweat joints leak?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jok, Jan 29, 2012.

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  1. jok

    jok New Member

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    Took on my first copper soldering job today -- replacing my bath tub faucet PBV. I practiced with some 1/2" pipe/fittings and got the technique down. What I didn't anticipate was the problems I'd have making the brass to copper connections. Now that I've dug through the forum threads, I see that this is not uncommon.

    I finally got all this done, cut in the new tree to the existing hot/cold supply, turned on the water to the house, and, by some miracle, no leaks. I was pleasantly surprised. However, now I'm nervous that I might not have done such a great job on some of the brass/copper joints. Maybe I didn't get the full capillary action to suck the solder into the joint, and maybe it's just ponded up around the lip of the fitting. I was fairly careful about cleaning, flux, and heating the fitting (not the pipe), and I'm confident in the copper-copper joints. It was just so bloody difficult to get the brass hot and I may have been forcing the solder a bit too close the flame to get it to melt.

    Question is -- should I be comfortable that if I don't have leaks now, I won't have them in 2 days, 2 weeks, or 2 years? In other words, are leaks always evident immediately?
     
  2. hj

    hj Moderator & Master Plumber Staff Member

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    quote; In other words, are leaks always evident immediately?

    No. I once had a customer whose bad joint did not fall apart until 25 years later when he hit it while putting a can of peas into the cupboard.
     
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  4. jok

    jok New Member

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    Thanks, HJ.

    Is that an example of something you've seen many times? Does it take an impact for the leak to show itself? Seems like sort of a fluke.

    I've jockeyed the pipes around to get them just right, installed plugs for testing, swapped the test cartridge plug for the mixing valve. Do you think this would have been enough to expose a weakness?

    If you think I should still be concerned, do I cut the valve out and install a new one? Can I reinforce the current joints?
     
  5. LLigetfa

    LLigetfa DIYer, not in the trades

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    When I had my HWT replaced, it started leaking the next day. Rather than call back the installer, I just cut it out and sweated in a new elbow. When I plumbed my house in '98 a pressure test with air revealed one leak in a sweated joint and one leak on a threaded joint. I didn't have water at the time to test for leaks and closed up the drywall on the faith of the air pressure test.

    You could always do a pressure test but if you have any marginal piping in the walls, it could bring it to a head.
     
  6. Terry

    Terry Administrator Staff Member

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    Most of the time, if the joint is bad, they leak right away.
    However, there is always the exceptions to the rule. They make life interesting.

    I've seen joints that weren't even soldered that held for a while.
    There was a condo project on Sandpoint that we air tested. We had eight plumbers working on it, and someone was forgetting to solder their caps. Those things were shooting off during the test and scaring the heck out of us.
     
  7. Gary Swart

    Gary Swart In the Trades

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    You can not go back and reinforce the joints. Once the water has been in the joint, the only think you can do to it is drain all of the water, then disassemble the joint completely, clean the old solder out of the fitting or use a new one, then redo the joint. Any moisture in the pipes will create steam when heated and a small amount of steam will prevent a good solder joint. It may hold for a time. I had a similar event as the one HJ described. I had a new supply line from the street into my basement installed by a professional company. The line terminated with a valve in the basement, and it held fine for several years. Then I had occasion to bump the valve with a step ladder. Instantly, I had a 1" copper pipe flooding my basement. Turned out the meter did not seal perfectly so I had a very small amount of water in the pipe. Just enough to prevent a good solder joint.
     
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    One thing DIY'ers often don't know or fail to take into account, is that when soldering, you MUST have at least one end of the pipe open to the atmosphere - i.e., that last piece must have a valve or some other opening when soldering or you'll have problems. What can happen is that the heat from soldering increases the air pressure in the pipe and can blow a hole through the solder in that joint to relieve it. But, if you have the end open (either a valve or further down the path somewhere), the air pressure won't rise and that won't happen.

    A brass fitting is larger, heavier, and takes more heat than a copper one, so that can make things harder to solder especially if using a propane torch which doesn't get as hot as MAPP or other pro tools. It can be done, but it's easier to then burn the flux out and mess things up.
     
  9. jok

    jok New Member

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    You guys are awesome. Thanks for all the speedy responses.

    In addition to being awesome, you've all scared the sh!t out of me. I was at work all day today wondering how much water would be in the crawlspace. Rushed home, and it turns out that everything is still fine. Passed a 24-hour leak test!

    I'd like to add a note for other DIYers that stumble on this thread with similar questions. In my rush home for work, I stopped into a plumbing contractor's office that was nearby. Explained my situation and asked if he would have been willing to sweat four 3-inch sticks of copper into a new brass mixing valve at his shop. I could then just tie that into the rest of the tree with couplings, thus, I'd only be soldering copper to copper. He was totally fine with it and fine with giving a free lesson. Could be a good option for someone comfortable sweating the copper joints but afraid to potentially ruin a $30 mixing valve and/or have a leak in the future. Also, avoids the worry of acquiring something other than the cheapo Home Depoo propane torch.

    Thanks again!
     
  10. dlarrivee

    dlarrivee New Member

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    In the future, don't stick any solder into the flame.

    Once the joint is hot enough, you pull the flame away from said joint... maybe invest in a different torch if you must.

    I've used a propane torch for 3/4" and 1/2" copper-to-brass connections successfully with some patience.
     
  11. Hackney plumbing

    Hackney plumbing Homeowner

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    This is simply false information.
     
  12. dlarrivee

    dlarrivee New Member

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    I don't know how true or false it is, but I've always done it because I'm planning to drain out all the water in the line first.
     
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Try it with a short section between stops that are closed...unlikely to happen in a large pipe run since the pressure change would be minimal, but in a short section? Yes.
     
  14. Hackney plumbing

    Hackney plumbing Homeowner

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    I can solder long or short pipes it doesn't have anything to do with air pressure I assure you.

    I'll solder a 1" long piece of 1/2" copper with a cap on each end or 100' long piece with caps on each end. No problem.
     
  15. Hackney plumbing

    Hackney plumbing Homeowner

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    I think what you mean to say is steam builds up pressure in the pipe and blows your solder out. Yes thats very true. And opening a valve close by can help prevent that,along with removing all the water but as we all know its difficult to get it DRY. I typically heat the pipes while they are still apart after I get all the water out. This dries the pipe out so i dont get steam spitting solder at me. Its not air,its steam.
     
  16. Terry

    Terry Administrator Staff Member

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    It's still pressure.

    Unless you open something up, the last joint will leak.
     
  17. Gary Swart

    Gary Swart In the Trades

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    Here's how I handled the replacement of the valve on the supply line I describe in my previous post. The meter insisted on leaking...not much, but enough to put water in the pipe. I make a swab of pieces of a towel attached to a heavy wire...coat hanger I believe. When all was in readiness, I inserted the swab into the pipe as deep as possible. I put the valve over the wire, fluxed the joint, and soldered the valve in place. The swab kept the water well away from the joint while I soldered. Then I pulled the swab out through the valve and the joint has been holding for about 10 years.
     
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  18. hj

    hj Moderator & Master Plumber Staff Member

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    air

    quote; This is simply false information. This is simply false information.

    It is NOT false information. It is true as far as it goes, but sometimes good technique can overcome the problem, especially when you cannot give a convenient "relief" point. I was removing the cap from a short 1/2" stub soldered into a closed valve. It must have leaked a bit of water into the stub because it took a lot of heat to melt the solder. But when it did, the cap came off like a superheated rocket, and just missed a waitress who was walking by. If it had hit her, she would have had a "brand" on her thigh.
     
  19. Hackney plumbing

    Hackney plumbing Homeowner

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    Its false information.

    Its not air pressure...its STEAM. BIG DIFFERENCE.

    You can solder DRY pipes in any lenght all day long with caps on each end. Air pressure has ZERO to do with it.

    It seems most pros dont even know that copper pipes can develop scale on the inside.......this scale holds moisture. What happens to moisture when its heated?

    I assure everyone it has NOTHING to to with AIR pressure in the pipe. STEAM STEAM STEAM
     
    Last edited: Jan 31, 2012
  20. bluebinky

    bluebinky Member

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    Hmmm ... I suppose the air in the pipe has already expanded by the time you apply the solder.
     
  21. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Basic gas laws...PV=nrT, or if you move things around P=constant*T. Increase T, increase pressure. Which gas affects which constant you use, but just like a hot air balloon rises because the air expands, it will increase pressure in a pipe if it is closed. the smaller the pipe, the hotter the whole thing gets, the higher you can get the pressure. Yes, water when it turns to steam is also an issue, but even steam increases pressure as you raise it's temperature; it's just that it expands radically when it goes from liquid to vapor, which adds to the overall problem. Basic first year chemistry...

    Generally, it's fairly easy to leave an end open. If you don't, the joint is at risk. Obviously, it may not get high enough all the time, but there are times when it will give you grief.
     
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